The invention concerns a method and equipment for the bidirectional transmission of information, whereby the transmission of information is implemented between devices that are partners in communication ("communicators"), which have both a transmitter and a receiver, and whereby the information is transmitted in the form of serial bits and the direction of flow of information is switchable.
With such a method, data transmission can be implemented between two communicators--such as a computer and a printer, for example--which are not connected by cable, using infra-red light or radio as the transmission medium. Methods such as this can also be used in connection with communication networks, whereby information can be exchanged between communicators which are connected by cable within a network and those which are not connected to the network by cable.
For bidirectional data transmission, Half-Duplex and Full-Duplex types of operation are used. Full-Duplex operation gives better performance, as information flows can be transmitted simultaneously in opposite directions and need be neither stopped nor stored intermediately. This type of operation, although desirable and in many cases necessary, cannot be used with methods of the type described above because of the missing transmission medium. One such technique known from the literature uses as a result Half-Duplex operation, whereby an intermediate storage of the data to be transmitted is used. Should one communicator be sending a data packet, and a second communicator have a need to transmit data during this time period, then this second communicator stores the information to be transmitted, and sends it only after the end of transmission by the first communicator. A characteristic of Half-Duplex operation is that the change of direction is normally undertaken only at the end of a data packet. The disadvantages are the additional cost of the necessary intermediate information storage and the complex communication protocol. Additionally it can often not be decided in advance how long the maximum datastream is which must be stored. Thus a determination of the memory capacity is not possible, and because of this the memory must be dimensioned far above the average storage requirement. In addition, transmission will of course be considerably dependent on the load on the transmission medium, and delayed by varying amounts.